Transformer.



, PATBNTEDfA'UG. 28, 1906. RGONRAD. i

TRANSPORMBR.

APPLIOATION FILED JAN. zo, 1964.

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- M/ JM mm y B Y r TToR/VEY PATENTED AUG. 28, 1906.

l F. CONRAD.

TRANSFORMER.

APPLICATION FILED JAN. 20, 1904.

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l BY

` ATTORNEY /Y/VVENTOR I UNITED sTATEs IDATEN` EEICE.

EE'ANKCCNEAD, or EDeEwooD PAEII, rE NI\IsrI.i/'ANIA, A'ssIeNoa TowEsTINeHoUsE ELECTRIC a MANUFACTURING COMPANY, A CCE- PORATIN OF PENNSYLVANIA.

TRANSFUBMER.

Specification of Letters Patent. i

Patented nag. 2e, 1906.

Appunti@ met January 20,1904. seran No. 189.911.

.To 1f/ZZ whomtt may concern..- '1

Be it known that I, FRANK CONRAD, a citizen of the United States, and a resident of Edgewood Fark, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Transformers, of which the following is a specification.

My invention relates to transformers for alternatingA electric currents; and it has for Its principal object the provision of a transfo'rme'r to be employed in connection with protective apparatus for alternating-current circuits which will maintain a suitable operating voltage for such apparatus through a wide variation of voltage in the main circuit.

In the accompanying drawings, Figure 1 is a diagram of o'ne end of analternating-current system of distribution in which my invention-is utilized. Figs. 2 and 3 are side elevations of two forms of core-plates which are embodied inmy transformer, and Fig. 4f,

is a view in frontelevation of a complete transformer constructed in accordance with my invention.

Protective apparatus such as that shown 1n Fig. 1 is described and claimed in an application, Serial N o; 189,903, iiled jointly by H. P. Davis and myself` of even date herewith, and 1 will therefore here describe such apparatus only so far as may b e necessary to set forth the relations in whichvmy present Invention may be used. Y

Transformers .1 and 2 have their primary windings respectively'connected'in series relation inthe line conductors 5 and'7 of a three-phase circuit 5 6' ,7, and similar transformers 3 and 4 have their primary windings respectively connected in series relationl in the line conductors 8 and 10 of a three-phase circuit 8 9 10, which operates in parallel with the circuit 5 6 7 to supply transformers'13 or other suitable translating devices. The secondarywindings of the series transformers 1, 2, 3, and 4 are connected in series with windings 14 of special relaytransformers 15, each having a third winding 16, which is energized only when the currents in the two windings 14 are unequal or when one -is reversed from its normal direction.

Ghanicaily connected and adapted to move a contact member 19 against either the one or the other of the stationary contact-terminals 20 and 21. The effect of the latter action is to complete the circuit of the battery 22 through the one or the other of two circuitbreaker tripping-coils 23 and 24S.

The voltage-windings 25 of the instrument 18 are supplied from the'secondary windings 26 of a special transformer 27, which embodies my present invention. The primary winding 28 of the transformer 27vmay be connected directly between two conductors of p each of the distributing-circuits, as indicated at the top of Fig. 1, or it may be placed in series with the secondary winding 29 of a transformer, the primary winding 30 of which is connected between two conductors of each distributing-circuit, as indicated at -the bottom of. Fig. 1. The latter arrangement is preferable when the voltage of the distributing-lines is hi h, since a reduced voltage may be' thus supp ied to the windings 28 `of the transformers 27.

The iron core of the transformer 27 coinprises three legs 31, 32, and 33, the firstnamed two of which are'provided, respectively, with the windings 26 and 28y and the? last-named with an air-gap 34C. The portion of the leg 31 which is surrounded by the winding 26 is reduced in width sufficiently to insure a cross-sectional area that is materially less than that of the remainder of the core, and the cross-sectional area of each of the legs 32 and 33 may be increased by placing additional punchings of the form shown in Fig. 3 on both..sides of the reviously-described punchings, substantial y as shown in Fig. 4, which represents a complete transformer. The punchings may be made and assembled in'any desired manner; but I have found it convenient to make punchings 35 of substantially E shape and of two dimensions as regards the length of the legs 31 and 32, as shown in Fig. 2, and punchings36 of sub-` stantially U shape and also of two different dimensions as regards the length of the leg 32, as shown in Fig. 3, and to assemble them to form the core by alternately reversing either single punchings or groups of punchings having similar dimensions. v Yin the event of a short circuit on either line the voltage would drop by reason of the IOO given operating voltage on any apparatus reexcessive current flowing, and if nodevice l such as I have described were employed the voltage supplied to the instrument 1S would be too low to operate it. In my transformer the iron ofthe reduced portion of the leg 31 is heavily saturated at the normal voltage of the line `and the remainder of the .flux induced by the primary winding 28 is forced across the air-gap 34 in the leg 33. If 'th voltage impressed upon the primary winding 28 is greatly reduced, a smaller quantity of i flux is forced across the air-gap 34, while that l threading through the winding 26 is only slightly reduced because of the smaller reluctance of that path. Hence the voltage impressed upon the windings 25 of the instrument 18 is varied but slightly, erven though the drop on the line is considerable.

Evidently it is possible to use my transformer as either a step-up or as a step-down transformer if it is desired to impress a higher or lower voltage on the windings of the instrument than can be derived from themain circuit ;A but it will generally befound advisable to employ another transformer for such purpose, as has been already indicated. It is also obvious that my invention is capable of adaptation to other uses than I have de scribed in which it is desired to maintain a gardless of variations in the voltage of the main circuit.

I claim as my invention# 1. A transformer-core which provides two magnetic circuits, one of a large cross-sectional area and interrupted by an air-gap, and the other of a much smaller cross-sectional area.

2. A transformer-core having three legs7 one of the outer legs having a smaller crosssectional area than the other two and the other outer leg being interrupted by an air- 3. A transformer-core which provides two magnetic circuits, one unsaturated and of high reluctance and the other saturated and of low reluctance.

4. A transformer having primary and secondary windings and two magnetic circuits passing through the primary winding, one unsaturated and of high reluctance, the other saturated, of low reluctance and surrounded by the secondary winding` 5. A transformer comprising -primary and secondary windings and an iron core having three legs, the primary coil being wound on the inner leg, the secondary on an outer leg having a smaller cross-sectional area than the other two, and the other outer leg being interrupted by an air-gap.

6. A transformer having primary and secondary windings7 a primary magnetic circuit of high reluctance and a primary magnetic circuit of relatively low reluctance which is also the magnetic circuit for the secondary winding.

7. A transformer having primary and secondary windings and two magnetic circuitsof different reluctancer only one of which is common to both primary and secondary coils.

8.' A transformer having primary and secondary coils and two magnetic circuits of respectively high and low reluctance, the latter being common to beth primary and secondary coils.

9. A transformer having primary and secondary windings and a core that embodies a magnetic circuit which is common to both windings andan independent magnetic circuit for the primary winding.

10. A transformer having primary and secondary windings and a core .having three legs, one of which has an air-gap.

1 1. A transformer having primary and sec ondary windings and a core provided with three legs of different cross-section.

12. A transformer having primary and secondary windings and a core provided with three legs of different cross-section, the largest leg being surrounded by the primary wind ing and the smallest leg being surrounded by the secondary winding.

13. In a system of distribution, the combination with a circuit-breaker having a tripcoil and a circuit-closing device having a current-coil and a voltage-coil, of a transformer for energizing the trip-coil comprising a core having three legs of different cross-section one of which has an air-gap and primary and secondary coils on the other legs.

14, In a system of electrical distribution comprising parallel lines, the combination with circuit-breakers having connected trip coils and a single circuit-closing instrument for both coils, having two current-windings and two voltage-windings, series transformers between the current-windings and the parallel lines and transformers between the voltage-windings in the lines each. of which has two legs for the respective windings and a third leg having an air-gap but no winding. v 15. A transformer comprising a core having three legs one of which is provided with an air-gap.

16. A transformer comprising a core hav- TOO IIO

ing three legs and primary and secondary- FRANK CONRAD.

I/'itnessesz Jos. W. ALEXANDER, BIRNEY Hrnns. 

